1. Field of the Invention
The present invention relates to a pulse combustion device, and more particularly to an improvement of a pulse combustion device adapted for use in a cooking instrument such as a cooking vessel or pot to heat cooling oil or water stored therein.
2. Discussion of the Prior Art
In a conventional pulse combustion device of this kind, flapper-type gas and air inlet valves are adapted to supply gaseous fuel and air into a combustion chamber, and a tailpipe is connected to an outlet port of the combustion chamber to take place therein resonant combustion of the mixture of gaseous fuel and air and to exhaust therefrom the combustion products. In FIG. 6, there is illustrated a portion of such a conventional pulse combustion device as described above which comprises a cylindrical support member forming therein a mixing chamber 1 in open communication with a combustion chamber (not shown), an end wall member 23 coupled with an open end of the support member, a cylindrical member 24 integrally secured in the center of end wall member 23 to form therein a gas passage in open communication with the mixing chamber 1, a flapper-type gas inlet valve unit 35 disposed within the cylindrical member 24 to permit inward flow of gaseous fuel passing therethrough from a gas container (not shown) into the mixing chamber 1 and to block outward flow of fuel-air mixture from the mixing chamber 1, and a flapper-type air inlet valve unit mounted to the end wall member 23 to permit inward flow of the air passing therethrough from an air intake chamber 7 into the mixing chamber 1 and to block outward flow of fuel-air mixture from the mixing chamber 1. The air inlet valve unit includes an air flapper valve 4 which reciprocates in a limited space between a valve plate 2 and a perforated backer plate 5 to open and close radial air inlet slots 3 in the valve plate 2 at a frequency of pulse combustion.
In operation of the conventional pulse combustion device, combustion products of high temperature flow reversely into the mixing chamber 1 through a flame trap (not shown) at every pulse combustion in the combustion chamber. The reverse flow of combustion products causes the air flapper valve 4 to be exposed to the high temperature of combustion products and to be abutted against the valve plate 2. This shortens the span of life of air flapper valve 4 and causes unwanted abutment noises. In the conventional pulse combustion device, except at starting thereof, the pressure in the air intake chamber is maintained at a constant value (about the atmospheric pressure), and the supply amount of air may not be decreased in accordance with a decrease of the supply amount of gaseous fuel. As a result, the supply amount of air becomes excessive, and the turn-down ratio is limited to around a value of 1/2.